Fever

by Warren P. Silberstein, M.D.
03/05/97

Fever is any elevation of the body temperature over 99.9ºF. It is one of the most common reasons for parents to visit the pediatrician with their children. High fever strikes fear in the hearts of most parents. The higher the fever the more frightening it is. Judging from the telephone calls I receive, most parents consider a rise in temperature from 103ºF to 103.5ºF worrisome and very significant. They must either believe that the rise in fever indicates that it will rise indefinitely or at least to a dangerous level, or they must consider 103.5ºF to be significantly more dangerous than 103ºF.

Pediatricians have a somewhat different view of fever. Infants below the age of 2 months don't have well developed immune systems yet, so any infant below 2 months with a fever could have a serious infection and should see his pediatrician immediately. For older infants and children we recognize that fever is not the enemy. Fever is just one sign of illness, and it isn't always the most important finding. In fact fever is beneficial in the body's fight against infection since most of the germs that cause infections in people are adapted to living at the normal human body temperature. Streptococcus doesn't like it's home to be 104ºF any better than you do.

Parents worry about fevers of 104ºF because they think that such a high fever is dangerous or can do harm to the body. While it is true that some children may have febrile convulsions at that temperature (which is enough to scare any parent), most children will never have a seizure with fever. And even though seizures with fever are frightening, they are not dangerous. A temperature of 108ºF is certainly likely to cause brain damage. Children can generally tolerate temperatures up to 106ºF without harm although such high fevers are not good for the health of parents. Fevers almost never go above 106ºF because the body produces the fever in response to illness and the body is usually smart enough to not hurt itself. Temperatures are more likely to go dangerously high if a child is dehydrated since he needs fluids to sweat to bring the fever down, or if the child has too much clothing or blankets since they will prevent heat from escaping, or if he has meningitis which can interfere with the thermostat in the brain.

Pediatricians take high fevers seriously because temperatures over 104ºF have a higher likelihood of being caused by a serious bacterial infection like pneumonia or meningitis. Our concern is not what the fever might do to our patient, but rather, what is causing the fever. A child who has a high fever deserves a thorough examination and may even require some tests like a complete blood count, chest x-ray, and urine culture, to help evaluate the cause for the fever. If the cause of the fever is not established with certainty and the fever remains high then the patient deserves careful observation and periodic reevaluation by the doctor.

Even though serious infections often cause high fevers, children can have high fevers for less worrisome reasons as well. Roseola often causes high fever, but typically children with Roseola don't act sick. The fever may last 4-5 days. The diagnosis of Roseola cannot be made until the end of the illness when the fever breaks and the rash develops. Children can run high fever with influenza and other viruses. Viruses cause illnesses like colds, chickenpox, gastroenteritis, and mononucleosis. Some can make children quite ill, but they generally run their course within 3-5 days (7 days for influenza) and then the children recover. Since viruses don't respond to treatment with antibiotics the usual treatment is just to relieve symptoms including fever.

Most childhood infectious illnesses cause other symptoms besides fever and these are just as important as fever to help you decide whether your child needs to see a doctor. If a child is extremely lethargic or extremely irritable these are both signs of more serious illness. A child who is vomiting and can't retain fluids or who experiences difficulty breathing needs to be seen for those symptoms. What it boils down to is that the seriousness of a child's illness cannot be gauged by the height of the fever.

Parents usually become aware that their child is sick when he becomes cranky, or takes an extra nap, or doesn't eat. Some illnesses may come on abruptly with pain or vomiting. But often the first thing a parent notices is that his child feels warm. While this is an excellent reason to suspect that a child has a fever, parents should be aware that feeling a child's body is not always a reliable way to judge a child's fever or even if he has a fever. When a child's temperature is rising the body conserves heat by decreasing the circulation to the skin. If you feel a child at that point in his fever he could feel relatively cool to the touch even though the fever may be significant. If a child is extremely ill or dehydrated he could also have decreased circulation to the skin and feel cool. On the other hand, when the temperature starts to come down, circulation to the skin may increase to allow heat to escape and the child may appear flushed and feel hot. If a child is wrapped with lots of blankets or has been very active this could also make his body feel hot.

If a child doesn't seem too ill and a parent doesn't suspect a very high fever it is okay to treat the fever without having a number, but the only reliable way to know what a child's temperature is is to use a thermometer. Temperatures can be taken using glass mercury thermometers, digital thermometers, or infrared tympanic membrane thermometers (ear thermometers). Fever strips that can be placed on the forehead are unreliable. Ear thermometers are somewhat controversial. Many studies suggest that they are the best measure of core temperature and parents love them because they are quick and easy. One problem is that they must be aimed at the ear drum. Even though they take quick readings this can be very difficult in an infant and missing the drum may result in missing a fever. Some of my patients have found repeat readings varying by as much as 3 degrees. Although most concerns about the ear thermometer revolve around falsely low readings, my experience has been that most of the calls I get about fevers over 105ºF have been taken with an ear thermometer. This may result from the ear thermometer giving higher readings but may also reflect a greater willingness of parents to take multiple readings in a sick kid using the ear thermometer.

Temperatures can be taken orally using the glass or electronic digital thermometer in any child who is able to cooperate in holding it under his tongue. The child should be instructed to close his lips on the thermometer like he is kissing it and not to bite on it. For the reading to be accurate the thermometer tip must stay under the tongue and the mouth must stay closed. If a child has had a cold or hot drink before his temperature is taken this can affect the oral temperature. Otherwise, if the child is cooperative, the oral temperature is pretty close to the rectal temperature.

Young infants can have their temperatures taken rectally or under the arm (axillary) with either a glass thermometer or an electronic digital thermometer. To approximate the rectal temperature you must add 2 degrees to an axillary reading.

Parents are often so anxious about fever that they feel they must wage an all out war against it and bring the fever down immediately. Children with higher fevers vomit more, have more headaches, and generally feel more miserable. But fever itself is rarely so high that it requires urgent action. Since fever is beneficial in the body's fight against infection our goal is not even necessarily to bring it down to normal, but just to bring it down enough to make the patient more comfortable. If a child's temperature does not return to normal after treatment there is no cause for worry. The fever will go away when the illness is over. Treating fever can make a child feel better, but it does not hasten his recovery.

One of the things that parents often do in an attempt to bring the fever down quickly is to put their child in a tub of water or give an alcohol rub. I always advise that parents allow the fever medicine at least an hour to work before resorting to such measures because fever medicine works by lowering the thermostat in the brain, and if you plunk a child in water to lower his fever without lowering his thermostat, the child will develop chills which will bring the fever back up and make the child uncomfortable.

Once the fever medicine has had a chance to work I recommend immersion in a room temperature tub for fevers that remain above 104ºF. Immersion works by conducting heat away from the body. The larger the volume of water there is in the tub, the more effective it is. People who are found in the water after airplane or boating accidents are often hypothermic (low body temperature) because large volumes of water can conduct a large amount of heat away from the body. Immersion is different from evaporation. Evaporation works by taking heat directly away from the skin. When you apply water to the skin and allow it to evaporate considerable heat can be taken from the skin, but that can result in chills before a significant amount of heat is removed from the core of the body. Alcohol is used because it increases evaporation, but the fumes of alcohol can be dangerous so even though Grandma may tell you that she used it on you, you should stay away from alcohol rubs and use immersion instead of evaporation.

Children with fever should be kept dressed lightly. Dressing a febrile child in heavy clothing or wrapping him in extra blankets will prevent heat from escaping when the fever is ready to go down and may cause the temperature to go higher. If a child has chills, you can give him extra blankets for his comfort until the chill has passed, but then all extra wraps must be removed. Children with fever need extra fluids. Since sick children often have a decreased appetite and may even vomit they should be given small amounts of clear fluids frequently. Feeding them is not important, but getting fluids into them is crucial.

Any child who has a high fever should be looked at by a doctor, especially if he is acting sick or has any other worrisome symptoms. But it is okay to treat a fever to make a child more comfortable until he can see the doctor. There are basically two medicines available for treatment of childhood fevers. Aspirin, which was popular when I was a child, should not be used because it can cause Reyes Syndrome. Acetaminophen (Tylenol, Tempra, Panadol) is very effective for treating fever and the miseries that come with illness. There are several dosage forms and they are not interchangeable. A child who takes a teaspoon of the elixir or syrup (160 mg./tsp.) would be seriously overdosed if he took a teaspoon of the drops (80mg./0.8 ml) and a child who usually takes a dropperful of the drops would be underdosed with a dropperful of the elixir. The dose of Acetaminophen is a maximum of 80 mg. per 12 pounds of body weight every 4 hours and no more than 5 doses in 24 hours. This is 1/2 teaspoon of the syrup (160 mg./5 ml) or 1 dropperful (0.8 ml.) of drops, or 1 chewable (80 mg.) per 12 pounds.
Acetaminophen
Drops, Syrup, & Chewables

Pediatric Dosage Chart

Dosage
AgeApproximate
Weight Range*
DropsSyrupChewables
80 mg
Chewables
160 mg
Under 4 moUnder 12 lb½ dropper
(0.4 ml)
¼ tsp
-
-
4 to 11 mo12-17 lb1 dropper
(0.8 ml)
½ tsp
-
-
12 to 23 mo18-23 lb1½ droppers¾ tsp
-
-
2 to 3 yr24-35 lb2 droppers1 tsp2 tablets
-
4 to 5 yr36-47 lb3 droppers1½ tsp3 tablets
-
6 to 8 yr48-59 lb
-
2tsp4 tablets2 tablets
9 to 10 yr60-71 lb
-
2½ tsp5 tablets2½ tablets
11 yr72-95 lb
-
3 tsp6 tablets3 tablets
12 yr & older96 lb & over
-
4 tsp8 tablets4 tablets
*If child is significantly under- or overweight, dosage may need to be adjusted accordingly

Acetaminophen (APAP, Feverall) is also available as suppositories in 80 mg., 120 mg., 325 mg. and 650 mg. strengths for the child who is vomiting.

Ibuprofen (Children's Motrin, Children's Advil) may be more effective for high fevers and severe pain. Ibuprofen keeps the fever down for longer periods, but it can be irritating to the stomach. The dose is 1 teaspoon (100 mg) per 22 pounds of body weight every 5-6 hours with a maximum of 400 mg. per dose and a maximum of 4 doses per day.

Please read all labels carefully before you give any medications. When you are upset about a child's illness it takes even more care to avoid making a mistake. Even though I hope I have made it easier for you to cope with your child's fever, if you feel worried about any symptom your child has, you should call your pediatrician.


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